Additional information as to angiographic and hemodynamic non-invasive laboratory data obtained from patients with arterial occlusive disease will be stored in our computer system and combined with our previously stored data a first comprehensive analytical attempt will be made to evaluate the sensitivity and specificity of each test separately as well as of the complete battery of four tests. Concentrated attention will be given to two different approaches to analyze skin perfusion - calibrated photoplethysmography and heat clearance. The more promising of these techniques will be selected to be incorporated in a panel of non-invasive tests to be used to study the upper extremity circulation in health and disease. Extracranial arterial disease will be studied by means of several types of spectral frequency analysis. It is expected that a successful completion of these projects will substantially improve our diagnostic capabilities in the area of peripheral arterial disease.